This invention relates to a numerically controlled embroidery machine having a work piece held by a hoop, or a clamp, and moved under a sewing head on an X-Y table which is driven along two perpendicular coordinate axes by two stepping motors; the said motors rotate to produce a predetermined pattern that is recorded within a computer memory; the said memory controls the stepping motor motion at the times the embroidery needle is out of working piece to be embroided.
Similar machines are described in the following U.S. Pat. Nos. 4,050,393 by Welcher et al.; 4,069,778 by Kozawa; 4,135,459 by Manabe et al.; 4,152,994 by Sugiama; 4,325,313 and 4,365,565 both by Kawai et al.; 4,444,134 by Matuyama et al.; 4,622,907 by Kimura.
Specifically, this invention relates to those parts of an embroidery machine that position material of a work piece, under a machine head, in a predetermined embroidery pattern. Contained in the above cited U.S. Patents there is described a set of embroidery machines. There are some improvements on the material feed mechanism for the said machine. The said mechanism in many cases is called a Pantograph.
The following patents describe the said pantographs: U.S. Pat. Nos. 4,186,673 by Vartoukian; 4,187,794 by Ross; 4,195,581 by Ohara; 4,444,133 by Bolldorf et al.; 4,598,655 by Takenoya.
In several patents one can see an intent to create a low inertia means to move the work piece with high speed during an embroidery process. For example, as it is described in U.S. Pat. No. 4,186,673 by Vartoukian. For this purpose, in several patents, stepping motors, are used to move a work piece in X-Y directions. The motors are rigidly attached to the machine frame, and the output motion of the stepping motors is transferred to a work piece mounted on a hoop by a wire running around a set of rollers. That arrangement is shown in units; U.S. Pat. No. 4,135,459 by Manabe et al.; in U.S. Pat. No. 4,186,673 by Vartoukian; in U.S. Pat. No. 4,201,144 by Manabe et al.; in U.S. Pat. No. 4,325,313 by Kawai et al.; in U.S. Pat. No. 4,598,655 by Takenoya.
Also, some patents show large and heavy pantographs to cover a big embroidery area. That is shown in U.S. Pat. No. 4,152,994 by Sugiama, in U.S. Pat. No. 4,444,133 by Bolldorf; in U.S. Pat. No. 4,495,876 by Tajima; and in U.S. Pat. No. 4,627,369 by Conrad et al.
A system to control embroidery stepping motors according to an embroidery pattern design and having the said pattern design recorded within a computer memory exists. Futhermore, systems exist which are capable of working with synchronization of other mechanical systems. These systems are applied to a number of different kind of pantographs with minor adaptations. These systems are described in the U.S. Pat. Nos. 4,152,994 by Sugiama; 4,309,950 by Franklin; 4,325,315 by Totino et al.; 4,526,116 by Mannel; 4,498,403 by Yanagi et al.; 4,683,827 by Kinoshita; 4,692,871 also by Kinoshita. The said systems use electronic computers to control mechanical output, hence very little time is required for any operational change to move a piece of work under a needle regardless of embroidery area involved, and also regardless of the desired quality of the embroidery pattern. The embroidery speed and/or embroidery quality in most cases is limited by deficiencies in mechanical assemblies engaged between stepping motors, from one side, and an embroidery hoop holding a piece of work to be embroided, from another side.
To demonstrate this, let us consider, first, all pantographs with wire transmission. Positively all of them must use a set of idling and direction control rollers; these rollers being dynamically rotated in both directions will increase inertia of machinery kinematics. This, causes the average speed of an embroidery operation to diminish. A wire works only for tension, being unable to transfer compressive force. By this reason, a wire working as a mechanical transmission device takes at least twice the length that would be needed by a solid unflexible linkage to transmit the same reciprocated motion. A wire causes a noticeable backlash during reciprocation, because the part of the wire transmission system under tension moves the hoop, while the idling part of the wire loop is generally free of any tension in order to minimize forces on the roller axes and thus prevent any significant increase of friction forces. In a large pantograph a wire transmission mechanism could create jolts and jiggling which is unacceptable for fine embroidery operation. Generally, small pantographs operating at slow speeds may employ a wire transmission.
As long as the embroidery industry grows, an increase in speed and range of embroidery operation will be a matter of competition in the specialized machinery market. Currently, some available embroidery pantographs having screw-and-nut couplings to transfer rotating motion into reciprocating motion look more promising for future embroidery machines than pantographs with a wire on rollers. Pulley-and-timing belt couplings may also be successfully utilized. Gear wheels with rack-and-pinion coupling also looks much better than a wire on rollers and pulleys. These types of pantographs are disclosed in the U.S. Pat. Nos.: 4,069,778 by Kozawa; 4,152,994 by Sugiama; 4,44,133 by Bolldorf et al.; 4,444,134 by Maruyama et al.; 4,627,369 by Conrad et al.
Let us consider, next, the second type of pantograph, having no wire as means of transmission. We have to notice that a requirement for a fine embroidery operation calls for a very small clearance between meshed transmission parts, however, small clearances create objectionable friction forces between the meshed parts. For a large operational area it is more desirable to have a low friction transmission. Thus, the market place should be highly receptive to a precision low friction embroidery mechanism. This is the first objective of this current invention.
As previously mentioned, all pantographs without a wire transmission have one stepping motor fixed to a immovable plate, and the second stepping motor fixed to a moveable plate; the moveable plate being driven by a transmission from the first stepping motor. This arrangement creates excessive weight and inertia within the moveable plate which must be overpowered by the first stepping motor during an embroidery operation.
The second purpose of the current invention is to allow the second stepping motor to be fixed to a moveable plate which results in a light and low inertia benefit for all parts that are fixed to the moveable plate of the pantograph assembly.